We seek to obtain a detailed understanding of the biochemical mechanisms involved in collagen biosynthesis and secretion and the control of these processes. We seek to determine how cells distinguish which proteins are to be secreted, which are to be retained intracellularly and whether there is a relationship between the structure of procollagen and its ability to be secreted. By manipulating the synthesis and structure of various membranes of the cell, we hope to clarify the relationship between these membranes and collagen secretion. We are attempting to isolate collagen mRNA, develop a reliable assay for its quantitation, and use this assay to determine whether transcriptional control is an important factor in the regulation of collagen synthesis. We are continuing our studies on the role of isoaccepting tRNA species in collagen synthesis and testing the possibility that such species can exercise control at the translational level. The possible effects of glucocorticoids on modulation of the quantity and types of collagen synthesized by tissues of the developing chick embryo are being investigated. Collagen is the most prevalent protein in the human body, composing about one-third of total body protein. Because of its widespread distribution and function, collagen is involved either directly or indirectly in many human disease, both hereditary and acquired. These range from relatively innocuous conditions such as excess scar formation, to the debilitating arthritides, to fatal diseases such as generalized scleroderma and diabetes. Basic understanding of normal collagen metabolism is fundamental to a rational approach to these diseases.